Design of efficient, cost effective three phase induction motors for ceiling fans in India

Abstract

In developing economies such as India, improving the efficiency of home appliances is of high priority in locations which are characterized by a weak electric distribution system. Ceiling fans are one of the most used home appliances in India. They typically operate for many hours, and since most of them are driven by inefficient, low cost single phase induction motors, the total power loss is nontrivial. To overcome the inefficiency of single phase induction motors, brushless dc motors have been increasingly used in ceiling fans to achieve high efficiency and power factor at multiple speed settings. However, they are more expensive than conventional ceiling fan motors due to the additional cost of permanent magnets and power electronic drive circuit. Three phase in contrast to single phase induction motors have proven to have a superior performance especially for high power applications.

From a manufacturing point of view, they are no more expensive to build than single phase induction motors. Also, three phase induction motors require no permanent magnets, which makes them economically attractive. To be able to use three phase induction motors in home appliances at variable speed, a power electronic drive is required to convert the single phase supply to three phase. The drive circuit can also be controlled to improve the input power factor. With the advancement of power electronic technology and integrated control devices, such motor drives can be made efficient and cost effective. This thesis explores the design and optimization of three phase squirrel cage induction motors for the application of ceiling fans in India, with the objective of achieving a balance between efficiency and cost. A detailed analytical model for a low speed, low power three phase squirrel cage induction motor is developed. The analytical model is validated using finite-element analysis.

This thesis also optimizes the motor design using genetic algorithms. The optimized design weighs 4.5kg and achieves 70% efficiency, which proves more efficient than existing ceiling fan motors in India. The optimized design is also validated in finite-element analysis. Finally, this thesis presents a simulation study of the motor drive implementation for the proposed three phase induction motor.